下列哪项是引起腹水最常见的病因
A．充血性心力衰竭B．肝硬化C．肾脏疾病D．腹膜疾病E．腹腔脏器破裂
参考答案：B
— I'm sure Andrew will win the first prize in the final.
— I think so. He ______ for it for months. [ ]
A. is preparing
B. was preparing
C. has been preparing
D. had been preparing
简述干扰素的概念、种类、功能与干扰素抗病毒机理。
